New studies have shown that the quality of sperm is decreasing in Western countries. Though there are many factors at hand that could explain the downward spiral (and perhaps the dropping U.S. fertility rates), the dip could be caused by increased TV viewing. That’s right — TV could be effecting your man’s sperm!

The Harvard School of Public Health investigated the relationship between TV time, physical activity and semen quality in over 189 men. The men were aged 18-22, of normal height and weight, smokers and nonsmokers and from New York. Researchers asked them how often (and how intensely) they exercised and how often they watched TV, DVDs or other videos.

Their research (which was reported in the British Journal of Sports Medicine) found that on average, men spent from five to 15 hours exercising and four to 20 hours a week in front of the television.

But how did they draw the parallel between TV and low sperm?

Researchers found that men who spent 20 or more hours a week in front of the TV had a sperm count that was an average of 44% lower than the other men who spent less time in front of the tube. Men that were active, researchers found, how a 73% higher sperm count than their couch potato counterparts. To conclude, the researchers found that being more active and watching less TV were both associated with a high sperm count and concentration.

And if you’re wondering how parking in front of the TV for hours can impede on your sperm counts, here’s how: researchers found that it is possible that increase scrotal temperatures from remaining in the sitting position too long can contribute to poorer-quality sperm, which doesn’t mean your man is less fertile. It means that staying active may help to keep sperm healthy.

Study author Audrey Gaskins of the Harvard School of Public Health Department of Nutrition said, “We know very little about how lifestyle may impact semen quality and male fertility in general, so identifying two potentially modifiable factors that appear to have such a big impact on sperm counts is truly exciting.”